ELASTIC GUMS 283 
of the rubbery curd has set. Then he dips the paddle into 
the creamy liquid again, and repeats the operation till suc- 
cessive layers form a cake of considerable thickness. The 
cake is then cut from the paddle, and hung up to dry until 
firm enough to pack for transportation. Crude rubber 
comes into the market also in the form of sheets, balls, or 
masses of various shapes; and is often mixed with a con- 
siderable quantity of clay, bark, and other impurities. 
Rubber was first made known to Europe in the report of 
Columbus’ second voyage, where the statement occurs that 
the Indians were found playing with elastic balls which 
bounced better than the “wind balls” of Castile. It was not, 
however, till after the middle of the 18th century that this 
elastic material came much into use. For many years it was 
scarcely more than a curiosity, serving in a practical way for 
little else than to rub out pencil marks. From this circum- 
stance it gained the name “rubber” and was ealled “india- 
rubber”’ because of its importation from the West Indies. 
Caoutchouc did not come from Asia till much later. 
As the unique properties of rubber—its unequaled elas- 
ticity combined with its great imperviousness to moisture— 
became more fully realized, effort was made to bring it into 
wide use. Thus, it was manufactured into elastic webbing, 
overshoes, waterproof garments, and various impervious 
fabrics. Such goods became popular for a while, but their 
use was much restricted by the fact that the best rubber ob- 
tainable was apt to harden and crack in cold weather, and tc 
soften or grow sticky insummer. Moreover, it was found that 
unprotected surfaces of pure rubber adhere; and that articles 
made of it were often worthless after a few months keeping, 
and were ruined by contact with oils. Much futile effort was 
expended to remedy these defects. Finally in 1844, Charles 
Goodyear, an American, announced his discovery that mixing 
a little sulphur with caoutchouc, and subjecting it to con- 
siderable heat, produces a substance that is even more elas- 
tic than pure rubber, is unchanged by any temperature be- 
tween —20° and +180°C., is less affected by oils or other 
solvents of the unchanged caoutchouc, does not become 
adhesive, and keeps well. This process of combining sulphur 
